This is an engine issue, and the fact that scripts fired from dialog are not nearly as reliable as a script outside of the dialog.... An unfortunate reality of KotOR modding, I am afraid - The more complex your dialog tree, with more conditionals, and lots of scripts attached to nodes, some of them are going to *wank*.
Not saying it is not solvable, but digging for the script in question may be tricky indeed.
Examine the dialog tree (you are the expert!!) and look in the "scripts that fire when spoken" field at the end of Cole's dlg tree. s9 included his source, so when you find that script, you can post the source if you like and we will see if there is any glaring error. Likely that it is just KotOR being KotOR.